A common method for the removal of a body part is ligation. Ligation is a process in which a band or cord is fastened to the body part to be removed in order to constrict it, thus cutting off the supply of blood and systemic support. The body part thereafter atrophies and drops away from the body. Ligation has been used for many purposes including castration and the removal of horns, tails or other body parts from animals.
Ligation has a number of advantages over surgical procedures for such applications. First, ligation has a safety advantage in that the animal normally does not become susceptible to infection. For example, in the case of castration of bulls, a period of about two weeks to a month typically passes between the time that the ligature is attached to the scrotum and the time that the scrotum drops off. During this time the area adjacent the ligature heals, thus reducing the likelihood of infection. Another advantage of ligation is that ligation can be performed quickly by non-expert personnel, thereby reducing costs. In addition, when the ligature is sufficiently tight, ligation can generally be performed with little stress on the animal because the body part numbs quickly after the blood supply is cut off.
According to one method of ligation, an endless loop of elastic band is used to cut off the blood supply to the body part to be removed. Because the band is endless, the band is positioned by passing the band loop over the body part. This method has the disadvantage that it is difficult to attach the ligature band such that it is sufficiently tight. For example, when an endless band is used to castrate bulls, the band must be stretched to pass over the scrotal sac and its contents and then released to engage the sac at the desired position. The tightness of the band when positioned is therefore limited by the band's elasticity. In addition, because an endless ligature band generally cannot be tightened, the size of the band loop can only be roughly matched to a particular application. That is, the band is usually selected from a limited number of discrete band sizes. Because of the difficulty in tightly applying endless bands, such bands may fail to sufficiently cut off the blood supply resulting in prolonged stress to the animal and an increased likelihood of swelling and/or infection. In addition, there is a greater chance that the animal will intentionally or unintentionally displace a loose band.
Another ligation method is disclosed in U.S. Pat. No. 4,691,704. A loop of a ligature elastomeric band is formed around the body part to be ligated, and then an end portion of the band is attached to a tightening rod. The tightening rod can then be retracted in a substantially linear fashion by successive pulls on a trigger mechanism, thereby tightening the loop. However, the process of tightening the loop through successive pulls on the trigger mechanism is time consuming and the animal must therefore be restrained for a longer period of time. In addition, the tension which can be imparted to the band, and the tightness of the loop, are limited by the hand strength of the user. Moreover, relatively large frictional and abrasive forces are exerted on the band where the band is attached to the tightening rod, thereby increasing the likelihood of damage to the elastomeric material causing breakage before the desired tension is achieved. Additionally, due to the design of the ligature tool, an operator is limited in the extent a band can be tightened. Once an operator has fully retracted the tightening rod, the loop's tightness cannot be increased.
The inability to achieve relatively quick and complete occlusion of both venous and arterial pressure within the body part being ligated may result in the venous pressure alone being shut off, thereby permitting the stronger arterial pressure to fill the bony part with blood. This, in turn, can lead to swelling of the body part and failure of the ligation process, causing consequential pain to the animal.